Safety control for rocker-arm welders



Oct. 30, 1951 J WELCH 2,573,124

SAFETY CONTROL FOR ROCKER-ARM WELDERS Filed May 5, 1950 I N V EN TOR. -16 ro/zze mZG/L Patented Oct. 30, 1951 SAFETY CONTROL FOR ROCKER-ARM WELDERS Jerome B. Welch, Wauwatosa, Wis., assignor to Cutler-Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Application May 3, 1950, Serial No. 159,694

7 Claims. 1

This invention relates to safety control for rocker-arm type welders.

In my Patent No. 2,494,847, issued January 1'7, 1950, there is disclosed a safety control system for powered welders which is particularly adaptable to welders of the ram type. The safety control herein disclosed is in certain respects similar to that disclosed in the aforementioned patent.

The object of the present invention is to provide for powered welders of the rocker-arm type control sensitive to obstruction between the movable electrode and the Work and responsive to move the movable electrode away from the work when an obstruction is encountered, while permitting normal operation of the welder under normal conditions.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawing illustrates a preferred embodiment of the invention which will now be described, it being understood that the embodiment illustrated is susceptible of Various modifications without departing from the scope of the appended claims.

The single figure of the drawing depicts more or ment and support therein, in any preferred manher, of a stationary welding electrode 8. 'ing bracket 9 secured to the top of the support 6 A bearis provided with a suitable clearance opening to accommodate a pivot shaft I0. Shaft II] affords pivotal bearing support for a movable carrier II and may be assumed to be supported adjacent its other end within another bearing bracket, not shown, which is like the bracket 9. Carrier H may thus be assumed to be freely movable about the shaft ID and constrained against any substantial lateral movement by said bearing brackets. A Welding electrode I2 is secured within the carrier I I adjacent the end of the latter overlying support 6 in any preferred manner, and upon pivotal anticlockwise movement of carrier II, electrode I2 is adapted to be brought into welding relation with the electrode 8 on the work I 3. Ad- J'acent its other end, carrier II is provided with a pin I 4 rigidly secured to and extending from a side thereof. Pin I I is accommodated within and projects through an elongated opening or slot I 5 2 formed in a member I6. Member I5 at its lower end is rigidly attached to a piston (not shown), which is adapted to move within the cylinder I! by application of air or fluid power to its opposite ends, and member I6 is thereby afforded rectilinear movement in reverse directions. Between the other end of carrier II and the pin I4, the carrier is reduced in vertical dimension to provide a reduced end portion. The reduced end portion is provided with a vertical clearance opening to freely accommodate the stem portion I8 of a switch actuator I9 which is preferably provided with a substantially spherical segment shaped end portion 20. Actuator I9 is biased downwardly in extended relation by a coiled compression spring 2I which bears at one end against the carrier I I and its other end against the inner side of portion 22. Stem I3 of actuator I9 is drilled transversely above the upper side of carrier I I to accommodate a cotter-key or the like to limit the extent of downward movement of stem 58 under the bias of the spring 2I. A tension spring 22 may be optionally attached at one end to member I 6 and at its other end it is secured to the carrier II.

As will be later more fully explained, the pin and slot connection between carrier I I and member I6, afforded by pin I4 and the slot I5 aforedescribed, provides a lost motion driving connection which facilitates the use of the control system now to be described.

The movement of member I 6 upwardly and downwardly is effected by the application of air or other fluid under pressure to the upper and lower ends of the aforementioned piston in cylinder I! through the conduits 23 and 24. The means for controlling the admission and release of air from said opposite ends of said piston comprise a well known form of multi-way valve 25 having an electromagnetic operating winding 26, and an auxiliary exhaust valve 21 having an electromagnetic operating winding 28, interposed in an exhaust conduit 29 which connects ihteriorly with cylinder I'l below the lower side of said piston. In conformity with general practice, valve 25 is biased to the position shown when its operating winding 26 is deenergized thereby affording connection of conduit 23 through said Valve with an air supply conduit 30 and connection of conduit 24 with an exhaust conduit 3|. The exhaust Valve 2! is closed when its operating winding 28 is deenergized and is opened by enerassociated with said carrier will be in the positions shown in the drawing.

An electric switch 32, which in one preferred form is a sensitive snap action switch of the socalled Micro type, is secured in any preferred manner to member I6. Switch 32 is provided with a stationary contact 32 a movable contact 321* which is normally disengaged from contact 32 and an actuator 32, which when moved inwardly of the switch effects, with snap action, engagement of contact 32* with contact 32 As will be later more fully explained, under certain conditions actuator 32 of switch 32 is adapted to be moved inwardly by engagement with the-end portion 20 of switch actuator I9.

An electric switch 33, which is preferably of the same type as switch 32, is secured in any preferred manner to the rear end of support 6. Swithch 33 is provided with a stationary contact .33 a-movablercontact 33 which .is normally-enfa ed with contact. 33 and an actuator 33, which when moved inwardlyof the switch, eifects with snap action disengagement of contact 23' from:contact 33 A switch actuator 34, adjustably supported in an arm 35 rigidly attached to member I6, is :adapted to effect operation of switch 33Iupon upward movement of member I6. Actuator 34 win a preferredtembodiment is provided with a casing 736 within whichis mounted in telescopic relation an operating member-31 which is norl-mallymrgeddn extended relation by a compres- 'siongspring 38 with respectto the casing 36. As rmember I,6moves:-upwardly, member 310i actuator 34 .ultimatel-y engages actuator 33 of switch 33to-lefiectactuation-of the latter. Further'upward movement of member I6 causes relative movement between member 3? and casing 36 of device 34 thereby :affording over-travel protec- -tiOI'I'fOI'rSWitCh .33. It may be assumed that the arm 35 is suitably formed andprovided-with fric- :tional clamping'means as will enable actuator 34 torbeiadjustablyvclamped therein so that the spacing between the upper end of member '31 :and the lower end tof actuator I330f switch 33 .may be adjusted.

The contact 33 of switch 33 connected to power supply'line L and thecontact 33 m said switch *is connected to contact 32 of switch 32. Contact 32 of switch 32 is connected -to supply line L through an electromagnetic operating winding 39 of a relay -39. A normally open switch AB, which inpraeticesis-preferably of the foot-operated type, :is connected across supply lines L and Win series with normally engaged rcontacts 39 gof relay 39 and operating winding #26 of valve .25. (Relay 39 is also provided with w-normally disengaged contacts 39' which when :engaged connects winding -28 of auxiliary -ex- ,haust valve '2'1 across supplylines L and L The operation -ofthe welder will now be described.

zand-airrin Jcylinder :I'I above the piston will be 1 exhausted through conduit 23, valve $2.5 and conduit 3 I. ,As-za resu1t,:member I6 moves upwardly. If :the :inherentbias 'or :turning moment of car- ;rier; I Izinclusivepfrelectrode I2tto'zthe: leftzof; pivot s'shaftrlill is .sufiiciently :great, r-which is :oftenztrue of many rocker-arm welders, carrier I I will move about pivot shaft I0 anticlockwise just as fast as the member I6 moves upwardly, thereby maintaining pin I l engaged with member I6 at the upper end of slot I5. In the event that carrier I I will not inherently turn anticlockwise fast enough to maintain such engagement between pin I l and member I6, it will belinsured by the tension spring 22 which resists relative movement between carrier II and member I6. In some instances the spring 22 may be dispensedwith if desired.

Assuming that there is no obstruction between the electrode I2 and work piece I3, carrier II will move anticlockwise just as fast as it is per- 'mitted to do so by member I6. Assuming that switch actuator 34 has been positioned in support '35 so that member 3'! is in properly spaced relation to the lower end of actuator 33 of switch 33 when member I6 isrin its lower extreme position shown in the drawing, member 3'!- will-then engage actuator 33 to effect actuation ,ofzswitch 33 just as, or slightly before, electrode I2rengages with the work I3. After electrode I2 has engaged the work I3, further movementof carrier I I will be momentarily arrested, and member I6 will then move with lost motion relative to carrier II (against 'the'tension of spring..22,if used) untilthe lowerend of slot I5 engages with pin I4 of carrier II. Upontake-up of the lost motion betweenmember I6 andcarrier II, electrode I2 willthen be-clamped against the -.,upper side of work piece I3 'under pressure imparted through member I6. Thereafter, it may be assumed thatthe welding electrodes 8'and I2 are suitably energized through an energizing circuit of any preferred type upon development of a predetermined degreeof pressure of-isuch electrodes against the work; the energizing ;means for electrodes ;8 and :I2 forming no part of the present invention.

After completion of vthe welding .of work I-3,-;the return of the welder'to its normal position Zisreffected by release of switchAD. Release-10f switch AIl causes winding 26 of valve 25 to be deenergized'and the :latter will assume its-normal operating position and air underpressure will be admitted to cylinder I"! on the upper side {of the piston and air will be exhausted from-thecylinder on the lower side ofthe piston. Consequently, member I6 willinitially move downwardly with lost motion with respect'to carrier II untilrthe upper end of slot I5 engages ,with'pin I I 01150211- rier ;I I Upon take-up of the' lost motionbetween member I6 and carrier II, the latter-will thentvbe pivotally moved in the clockwise directionqby member I6 until "said member and said Carrier return to their normalpositions shown'init-he drawing.

As will now be described, the -.control'system inherently functions in a -manner t prevent .in-

jury'tothe operator. Assume thatrduringroperw tion I of the welder to move electrode I2 "downwardly toward the worktheoperator negligently places'his hand over theworkin'line with'elec- TtlOdQ'lZ. Whenthe tip ofelectrode I12:comes into 'contact-with'the operators hand, movement :of carrier :II in the anticlockwise direction is arrested'with thelresult that member It thenmoves upwardlyiwithlost motion relative torcarrieril I. Upon a slight degree of such'lost motion move- 'ment, actuator 32 of switch 32. engages with-the ".endl ortionlfi of actuator I-Q andis moved inwardly of switch BEtOfGffGCt engagement of contact 132- with :contact 1.32 :Actuationof switch 39 of relay 39 to line L 32 thereby completes a circuit from line L, through switches 33 and 32, energizing winding Consequently, relay 39 functions to open its contacts 39 and close its contacts 39. As a result, winding 26 of valve 25 is deenergized, whichas aforedescribed, causes valve 25 to assume its normal position affording exhausting of air from the lower side of the piston and application of air to the upper side of the piston. Simultaneously therewith, the winding 28 of exhaust valve 21 is energized to afford supplemental exhaustion of air from the lower end of the piston. Member [6 is thereby caused to move rapidly in the downward direction and after take-up of the lost motion between it and carrier II, the latter i caused to be moved clockwise rapidly with the result that electrode 12 is moved rapidly away from the operators hand, before any appreciable pressure is exerted thereon, thereby preventing injury to the operator.

It will be appreciated that the safety function of the control system will be afforded so long as the switch S3 is not actuated prior to actuation of switch 32. To insure that such safety functions will be afforded up until the time the electrode I2 contacts or closely approaches the work, it is required that care be exercised in setting the position of actuator 34 in the support 35 to insure that switch 33 will not be operated appreciably in advance thereof.

In normal operation of the welder where no obstruction is encountered, the switch 33 will be actuated before switch 32 is actuated, thereby rendering the safety function inoperative. Switch 32 even during such normal operation will be actuated as a result of take-up of lost motion between member l6 and carrier H and the resiliently mounted actuator l9 affords over-travel protection for this switch.

Auxiliary exhaust valve 2'! and the parts associated therewith, including the contacts 39 of relay 39, may be omitted as desired if valve 25 is of such character that it will provide for exhaustion of air or other fluid at a rapid rate. The use of auxiliary valve 21 insures that there will be rapid exhaustion of air or fluid from the lower Side of the piston when a foreign object is encountered by electrode [2 in moving downwardly toward the work. i

I claim: I

1. In a powered electric welder, in combination, a pair of relatively movable welding electrodes, a carrier pivotally movable in reverse directions to move one of said electrodes toward or away from the other electrode, a rectilinearly movable member having a lost motion driving connection with said carrier, and which upon movement in one direction effects movement of said carrier to separate said electrodes, power responsive means affording movement of said member in said one direction to a normal extreme position or in the opposite direction toward another extreme position, said carrier having bias maintaining take-up of lost motion between it and said member upon movement of the latter from its normal extreme position toward its other extreme position untilthe carrier electrode contacts the work between said electrodes or is arrested before it contacts thework, and control means for said power responsive means including means responsive to relative movement between said carrier and said member resulting from arrest of the carrier electrode before it contacts the work to effect powered movement of said member in said one direction.

2. In a powered electric welder, in combination, a pair of relatively movable welding electrodes, a carrier pivotally movable in reverse directions to move one of said electrodes toward or away from the other electrode, a rectilinearly movable member having a lost motion driving connection with said carrier, and which upon movement in one direction effects movement of said carrier to separate said electrodes, power responsive means affording movement of said member in said one direction to a normal extreme position or in the opposite direction toward another extreme position, said carrier inherently tending to move its electrode toward said other electrode and insuring take-up of lost motion between it and said member upon movement of the latter from its normal extreme position toward its other extreme position until said carrier electrode contacts the work between said electrodes or is arrested before it contacts the work, and control means for said power responsive means including means responsive to relative movement between said carrier and said member resulting from arrest of the carrier electrode before it contacts the work to effect powered movement of said member in said one direction.

3. In a powered electric welder, in combination, a pair of relatively movable welding electrodes, a carrier pivotally movable in reverse directions to move one of said electrodes toward or away from the other electrode, a rectilinearly movable member having a lost motion driving connection with said carrier, and which upon movement in one direction effects movement of said carrier to separate said electrodes, power responsive means affording movement of said member in said one direction to a normal extreme position or in the opposite direction toward another extreme position, resilient means associated with said carrier and said member for maintaining takeup of lost motion therebetween upon movement of the latter from its normal extreme position toward its other extreme position until the carrier electrode contacts the work between said electrodes or is arrested before it contacts the work, and control means for said power responsive means including means responsive to relative movement between said carrier and said member resulting from arrest of the carrier electrode before it contacts the work to effect powered movement of said member in said one direction.

4. In a powered electric welder, in combination, a pair of relatively movable welding electrodes, a carrier pivotally movable in reverse directions to move one of said electrodes toward or away from the other electrode, a rectilinearly movable member having a lost motion driving connection with said carrier, and which upon movement in one direction effects movement of said carrier to separate said electrodes, power responsive means affording movement of said member in said one direction to a normal extreme position or in the opposite direction toward another extreme position, said carrier having bias maintaining take-up of lost motion between it and said member upon movement of the latter from its normal extreme position toward its other extreme position until the carrier electrode contacts the work between said electrodes or is arrested before it contacts the work, and control means for said power responsive means including in association with said member and said carrier cooperating electric switches which as a function of'relative movement between said carrier d. said member resulting from arrest. of the carrierelectrode before it contacts thework effect powered movement of said member in said one direction. 5. in a powered electric welder, in combination, a pair of relatively movable welding electrodes, a carrier pivotally movable in reverse directions to move one of said electrodes toward or away from the other electrode, a rectilinearly movable member having a lost motion driving connection with said carrier, and'which upon movement in one direction effects movement of said carrier to separate said electrodes, power responsive means afiording movement of said memberin said one direction to a normal extreme position or in the opposite direction towardanother extreme position, said carrier having bias maintaining take-up of lost motion between it and said member upon movement of the latter from its normal extreme position toward its other extreme position until the carrier electrode contacts the work between said electrodes or is arrested before it contacts the work, and control means for said power responsive means acting upon relative movement between said carrier and said member resulting from arrest of the carrier electrode before it contacts he wo o efi ctnowered, mo e ent of s membe n said, one ir ctic ai con r m a 19 ca in it te iu c pn. m s e coope atin electric witch s ne oi hi h i on rable as an incident to relative movement between saidcarrier and said member and another of whichis operable, as a function of a predetermined distance travel, of said member from its nor al qsiticn.

5'- P w 6 59 1 9 Wa en. 9 1 91 on a Pai i r a v y mo a el in lsetr des C ivo y I mo le in r v r e directions to move one of said electrodestoward a r he o e le t ode a re ti n rly movable member having a lost motion driving o n c w h a rrier and whi h 1.901? movementin one direction effects movement of said carrier to separate saidelectrodes, power responsive means afiording movement of said member in said onedirection to a normal extreme position or'i n the opposite direction teward another extreme position, said carrier having bias maintaining take-up of, lost motion between it, and said member upon movement of the latter from its normal extreme position to-v ward its other extreme position until the carrier eleetrodecontacts the work betweensaidelectrodes or is arrested before it contacts thework, and control means for said power responsive means comprising in series relation first. and second single throw electric switches, said, first switch being operable to complete a circuit upon relative movement between said carrier and said member when the latter is moved toward its other extreme position, said second switch being normally positioned to complete a circuit such that circuit closing operation of said first switch will cause said control means to efiect powered movement of said member in said one direction, and said second switch being operable as an incident to predetermined distance travel of said member from its normal toward its other extreme position to render circuit closing operation of said first switch ineffective.

7. In a fluid powered electric welder, in combination, a pair of relatively movable welding electrodes, a carrier pivotally movable in reverse directions to move one of said electrodes toward or away from the other electrode, a rectilinearly movable member having a lost motion driving connection with said carrier, and which upon movement in one direction effects movement of said carrier to separate said electrodes, fluid power responsive means subject to manual control to selectively move said member in said one direction to a normal extreme position or in the opposite direction toward another extreme position at will, said carrier having bias maintaining take-up of lost motion between it and said member upon movement of the latter from its normal extreme position toward its other extreme position until the carrier electrode contacts the work between the electrodes 0): is arrested before it contacts the work, an electroresponsive relay which when energized effects powered movement of said member in said one directionand first and second single throw electric switches in series relation, said first switch being operable to complete a circuit upon relative movement between said carrier and said member when the latter is moved toward said other extreme position, said second switch being normally positioned to complete a circuit such that circuit closing operation of said first switch will effect energization of said relay, and said second switch being operable as an incident to predetermined distance travel of said member from its normal toward its other extreme position to render circuit closing operation of said first switch, ineffective to energize said relay.

JEROME B. WELCH.

No references cited. 

